Magnesium monitoring practice in monoclonal anti-epidermal growth factor receptor antibodies therapy

It is now estimated that about 5% of cetuximab-treated patients and about 3% of panitumumab-treated patients will develop grade 3-4 hypomagnesemia. The aim of this study was to assess the extent of magnesium monitoring in patients treated with epidermal growth factor receptor (EGFR)-targeting antibodies and to estimate the incidence of hypomagnesemia in these patients at our institution.

A 2-year retrospective study was carried out. At least four doses of weekly cetuximab or two doses of bi-weekly panitumumab were required for inclusion. Serum magnesium profiles were reviewed from 1 month before treatment until 3 months after treatment discontinuation, and patients with <2 determinations were excluded.

Two hundred and one patients received at least one dose of EGFR-targeting antibodies, but only 68 met the inclusion criteria. Seventy patients had <2 magnesium determinations. The overall hypomagnesemia was 58·82% (40 of 68 patients), with a 4·41% grade 3 hypomagnesemia (three of 68 patients). No grade 4 hypomagnesemia was detected.

There is a lack of magnesium monitoring in these patients. Serum magnesium determinations should be done every 4-8 weeks in patients treated with EGFR-targeting antibodies, as it is a useful surrogate marker for both toxicity and efficacy.